A user places an enormous amount of stress on the spine when situated in a seated position. Prolonged sitting in the same position can cause fatigue, stiffness and severe back pain due to stress and strain on the ligaments and intervertebral disks of the spine. Supporting the lumbar curve of the spine reduces the load on the low back muscles. Lumbar supports, such as cushions, bladders and mechanical devices, have been widely adopted and integrated into many seating systems available today.
Gradually changing the position of the lumbar spine allows the various spinal muscles and ligaments to share the load of the upper body. Further, spinal movement can create changing pressure patterns within the intervertebral discs, facilitating circulation of fluid-borne nutrients and metabolites in and out of the discs. Continuous movement of the spine is known to increase flexibility and hydration of the disks, with the potential to prevent degeneration while decreasing stiffness and pain. Spinal motion is ideally accomplished while the head is maintained in a relatively stable position that allows steady visual contact for task performance. Intermittent soft-tissue compression may further comfort the user through a massage effect. The applicant has been issued U.S. Pat. No. 4,981,131 (hereinafter “the ′131 patent”) related to continuous passive motion (CPM), the teachings of which are herein incorporated by reference. The ′131 patent discloses an apparatus for cycling the lumbar region of the spine through a substantial range of lordosis (forward spinal curvature) for the purpose of relieving low back pain. In that patent, an inflatable bladder in contact with the back is pressurized and depressurized to affect the substantial range of lordosis.
There was no provision, however, in the ′131 patent for the user to apply, adjust, and control the force applied to the back without the input of electricity into the apparatus of the invention. The ′131 patent disclosed DC voltage input to a processor board which controlled and processed information from the pump, valve, and pressure transducer. Through extensive experience with CPM technology, the inventor has discovered that individual users require or prefer varying amounts of maximum and minimum pressures, rates of applied force, and lengths of applied force. It has further been found that movement of the spine may be increased if the movement of the lower extremities increases. Need, therefore, exists to allow a user to freely control the force rate and length of time, and amount of pressure applied to the spine and soft tissues. Further, a need exits to allow the user such control over spinal motion without the necessity of electric power and while encouraging lower extremity movement.
It is one object of the invention to provide a means and method of reducing fatigue, stiffness and severe back pain due to stress and strain on the ligaments and intervertebral disks of the spine caused in the seated position. More particularly, it is an object of the invention to support the lumbar curve of the spine and apply motion to the lumbar region of the spine and intermittent compression of the soft tissues. Further, it is an object of the invention to maintain a relatively stable position of the eyes and head to allow for task performance, but encourage lower extremity movement, while applying motion to the lumbar region of the spine.